Aggravation of experimental glomerulonephritis by superimposed clip hypertension

Acute kidney injury and chronic kidney disease: an integrated clinical syndrome

The previous conventional wisdom that survivors of acute kidney injury (AKI) tend to do well and fully recover renal function appears to be flawed. AKI can cause end-stage renal disease (ESRD) directly, and increase the risk of developing incident chronic kidney disease (CKD) and worsening of underlying CKD. In addition, severity, duration, and frequency of AKI appear to be important predictors of poor patient outcomes. CKD is an important risk factor for the development and ascertainment of AKI. Experimental data support the clinical observations and the bidirectional nature of the relationships between AKI and CKD. Reductions in renal mass and nephron number, vascular insufficiency, cell cycle disruption, and maladaptive repair mechanisms appear to be important modulators of progression in patients with and without coexistent CKD. Distinction between AKI and CKD may be artificial. Consideration should be given to the integrated clinical syndrome of diminished GFR, with acute and chronic stages, where spectrum of disease state and outcome is determined by host factors, including the balance of adaptive and maladaptive repair mechanisms over time. Physicians must provide long-term follow-up to patients with first episodes of AKI, even if they presented with normal renal function.

Estradiol reverses renal injury in Alb/TGF-beta1 transgenic mice

BACKGROUND

Men with chronic renal disease progress more rapidly to renal failure than do women. Tranforming growth factor-beta (TGF-beta) plays a central role in promoting progressive renal injury, in part due to transcriptional effects mediated by cooperation between Smad proteins and the transcription factor Sp1. Estrogen negatively regulates Sp1 activity and reverses the stimulatory effects of TGF-beta on type IV collagen synthesis and cellular apoptosis in cultured mesangial cells. We hypothesized that the ability of estradiol to reverse the effects of TGF-beta underlies gender dimorphism in the progression of chronic renal disease.

METHODS

We studied Alb/TGF-beta transgenic mice, which overexpress TGF-beta1 and develop proteinuria and progressive glomerulosclerosis. We implanted a sustained-release estradiol pellet or a placebo pellet into control and Alb/TGF-beta transgenic mice at 2 weeks of age. Animals were sacrificed at 5 weeks, at which time urine, blood, and renal tissue were obtained for study.

RESULTS

The sustained-release estradiol pellet achieved a physiologic concentration of estradiol. TGF-beta levels were higher in estradiol-treated mice compared to placebo-treated mice. Proteinuria was reduced in estradiol-treated Alb/TGF-beta mice compared to placebo-treated transgenic mice. Mesangial expansion and closure of capillary loops with enhanced glomerular deposition of type I collagen, type IV collagen, and tissue inhibitor of metalloproteinase (TIMP-2) was observed in glomeruli of placebo-treated transgenic mice. Estrogen therapy reversed these abnormalities.

CONCLUSION

Administration of estradiol to Alb/TGF-beta transgenic mice, which overexpress TGF-beta, ameliorated progressive renal injury. The ability of estradiol to reverse the pro-fibrotic effects of TGF-beta, both in vitro and in vivo, may underlie the sexual dimorphism in renal disease progression observed in humans.

Hypertension increases expression of growth factors and MHC II in chronic allograft nephropathy

BACKGROUND

Hypertension of the recipient is strongly associated with chronic allograft nephropathy. It is unclear, however, whether hypertension is the cause or the consequence of chronic allograft nephropathy.

METHODS

The present study was performed in the Fisher to Lewis rat kidney transplant model. Transplanted rats (N = eight in each group) received either no treatment or were made hypertensive by administration of deoxycorticosteron acetate (DOCA) and salt. Proteinuria and systolic blood pressure was measured monthly, grafts were harvested at 3 and 6 months for semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and for immunohistology.

RESULTS

Systolic blood pressure was markedly elevated in rats receiving DOCA/salt. Allografts of hypertensive animals contained significantly more cells expressing the proliferating cell nuclear antigen compared to isografts and to allografts from normotensive animals (P < 0.05). Histologic staining and mRNA expression of major histocompatibility complex (MHC) II was markedly increased in allografts of hypertensive animals compared to all other groups (P < 0.05). Expression of mRNA for platelet-derived growth factor-B (PDGF-B), transforming growth factor-beta (TGF-beta) and collagen was higher in allografts than in isografts and was highest in hypertensive animals.

CONCLUSION

We conclude that hypertension augments the expression of growth factors in the allograft possibly aggravating the intimal hyperplasia observed in chronic allograft nephropathy. By increasing the expression of MHC II antigens, hypertension may render the allograft more susceptible to alloantigen-dependent damage. Hypertension and alloantigen-dependent factors appear to exert additive or synergistic effects on inflammatory pathways leading to graft injury.

Renovascular hypertension does not influence repair of glomerular lesions induced by anti-thymocyte glomerulonephritis

BACKGROUND

Systemic hypertension is a risk factor for progression of renal disease. However, it is not clear whether hypertension has an effect on healing or regression of immune-mediated glomerular damage. To evaluate this effect, we applied a model of glomerulonephritis in rats with two-kidney, one-clip hypertension and studied the effect of hypertension on the healing process of this nephritis.

METHODS

The anti-thymocyte serum (ATS) glomerulonephritis was induced in rats six weeks after initiation of two-kidney, one-clip hypertension, when blood pressure was already increased. Renal structure and function were examined six weeks later. Glomerular expression of alpha smooth muscle actin, the cell cycle inhibitor p27Kip1, and transforming growth factor-beta (TGF-beta) was evaluated by Western blotting. Glomerular proliferation, monocyte infiltration, and fibronectin were examined by immunohistochemistry.

RESULTS

Decreased survival, an increase of proteinuria, as well as increased glomerular and tubulointerstitial damage, were found in hypertensive rats compared with normotensive rats. Expression of fibronectin, alpha-smooth muscle actin, TGF-beta, and p27Kip1 was increased in the nonclipped kidney. Complete healing of the glomerular changes associated with the nephritis occurred in normotensive nephritic rats. Surprisingly, complete healing of the nephritis was also found in the clipped as well as nonclipped kidneys of renovascular hypertensive rats. No significant differences could be found for survival, proteinuria, glomerular size, proliferation, monocyte/macrophage infiltration, sclerosis, tubulointerstitial damage, as well as expression of alpha-smooth muscle actin, TGF-beta, fibronectin, and p27Kip1 between hypertensive rats with and without nephritis.

CONCLUSION

These data demonstrate that renovascular hypertension does not influence healing of the glomerular lesions in the anti-thymocyte serum nephritis. This is a rather surprising observation and leaves the question open of which role, in fact, blood pressure may have on the reparative phase of an acute glomerulonephritis, or whether its role depends on the type of glomerulonephritis.

Lack of endothelial nitric oxide synthase aggravates murine accelerated anti-glomerular basement membrane glomerulonephritis

Nitric oxide (NO) radicals generated by endothelial nitric oxide synthase (eNOS) are involved in the regulation of vascular tone. In addition, NO radicals derived from eNOS inhibit platelet aggregation and leukocyte adhesion to the endothelium and, thus, may have anti-inflammatory effects. To study the role of eNOS in renal inflammation, the development of accelerated anti-glomerular basement membrane (GBM) glomerulonephritis was examined in mice lacking a functional gene for eNOS and compared with wild-type (WT) C57BL/B6j mice. WT C57BL/6j mice (n = 12) and eNOS knockout (-/-) mice (n = 12) were immunized intraperitoneally with sheep IgG (0.2 mg in complete Freund's adjuvant). At day 6.5 after immunization, mice received a single i.v. injection of sheep anti-mouse GBM (1 mg in 200 microl PBS). Mice were sacrificed at day 1 and 10 after induction of the disease. All WT mice survived until day 10, whereas 1 eNOS-/- mouse died and 2 more became moribund, requiring sacrifice. At day 10, eNOS-/- mice had higher levels of blood urea nitrogen than WT mice (P < 0.02), although proteinuria was comparable. Immunofluorescence microscopy documented similar IgG deposition in both WT and eNOS-/- mice, but eNOS-/- mice had more extensive glomerular staining for fibrin at day 10 (P < 0.007). At day 10, light microscopy demonstrated that eNOS-/- mice had more severe glomerular thrombosis (P < 0.003) and influx of neutrophils (P < 0. 006), but similar degrees of overall glomerular endocapillary hypercellularity and crescent formation. In conclusion, accelerated anti-GBM glomerulonephritis is severely aggravated in eNOS-/- mice, especially with respect to glomerular capillary thrombosis and neutrophil infiltration. These results indicate that NO radicals generated by eNOS play a protective role during renal inflammation.

Effect of renovascular hypertension on experimental glomerulonephritis in rats

Systemic hypertension is a major risk factor that determines the rate of progression of kidney disease. The underlying mechanisms, however, are incompletely understood. To gain insight into these mechanisms, the present study was undertaken to characterize the effects of renovascular hypertension on the course of anti-thymocyte antibody-induced glomerulonephritis. Glomerulonephritis was induced in rats 6 weeks after the initiation of two-kidney, one-clip hypertension, when blood pressure was already increased. Structure and function of the clipped and the nonclipped kidney were examined 5 days later. Glomerular filtration rate (GFR) was measured by inulin clearance. The induction of nephritis did not alter the blood pressure in either hypertensive rats or normotensive controls. Albuminuria increased slightly in normotensive rats after the induction of nephritis, whereas no significant differences were found between hypertensive rats with or without nephritis. No significant differences were found for the GFR values of normotensive controls and nephritic animals or for values in the clipped kidney with or without nephritis. However, the GFR of the nonclipped kidney was significantly reduced in nephritic animals as compared with all other groups. Morphologic evaluation revealed that hypertensive rats with nephritis exhibited a combination of characteristics of nephritis and hypertensive glomerular injury. Histologic findings of nephritis, such as glomerular binding of rabbit IgG and glomerular proliferation and mesangial matrix expansion, were similar after the induction of nephritis in controls and in the clipped and nonclipped kidneys of hypertensive animals. However, intraglomerular microaneurysms were significantly more often found in the non-clipped kidneys after the induction of nephritis. Hypertension-induced deterioration of glomerular function was not associated with marked morphologic deterioration but rather with a combination of the characteristics of nephritis and hypertensive glomerular injury.

Anti-GBM glomerulonephritis in mice lacking nitric oxide synthase type 2

Nitric oxide is synthesized in experimental immune complex glomerulonephritis due to local induction of type 2 nitric oxide synthase (NOS2). To determine the role of NOS2, the course of accelerated anti-glomerular basement membrane glomerulonephritis (anti-GBM) was examined in mice homozygous for disruption of the NOS2 gene compared with heterozygous littermates. Disease in the wild type strain (129Sv) was characterized by heavy albuminuria, glomerular neutrophil and macrophage infiltration and glomerular thrombosis. NOS2, interleukin 1B (IL-1 beta) and tumor necrosis factor alpha (TNF alpha) mRNA were induced by 24 hours. The NOS2-deficient mutant mice and the heterozygous mice displayed early (24 hr) and full autologous phase (day 6) injury indistinguishable from the wild-type mice. The equivalent degree of albuminuria and glomerular inflammation indicates that NOS2 does not play an essential role in this form of glomerulonephritis in the mouse.

Effect of enalapril therapy on glomerular accumulation of immune complexes and mesangial matrix in experimental glomerulonephritis in the nonhuman primate

The present study is a prospective, controlled, blinded trial of enalapril therapy in experimental immune complex (IC)-mediated glomerulonephritis (GN) in the nonhuman primate (cynomolgus monkey [CYN]). Two groups of CYNs were studied: those with established GN (study A) and those in which GN was being induced (study B). In study A, 12 CYNs had GN established by 8 or 10 weeks of daily intravenous infusion of bovine gamma-globulin (BGG). These CYNs were then assigned to either 4 weeks of daily oral enalapril therapy (n = 6) or daily oral placebo therapy (n = 6). The daily BGG infusions were continued during the 4 weeks of enalapril or placebo therapy. At the start of the enalapril/placebo protocol, the two groups were similar with respect to proteinuria and level of precipitating antibody to BGG, which determined the daily BGG dose. Renal biopsy was performed in each CYN at the start and end of the 4-week period of enalapril/placebo protocol. In study B, 15 normal CYNs were immunized to BGG over a period of 4 weeks. The CYNs were then assigned to daily oral enalapril therapy (n = 8) or placebo therapy (n = 7) based on level of precipitating antibody to BGG. At this point, daily intravenous BGG was begun along with daily enalapril or placebo for 8 weeks. Renal biopsy was performed in each CYN before and at the end of this 8-week period. In study A, enalapril therapy was associated with a significant decrease in mesangial matrix volume (mean change, -27.7%; P = 0.031) and a trend toward decreased mesangial matrix deposits (mean change, -34.1%; P = 0.188). By contrast, in CYNs receiving placebo therapy, mesangial matrix volume increased compared with the enalapril group (P = 0.002) and mesangial deposits were unchanged. In study B, both the enalapril and placebo groups showed significant increases in mesangial matrix volume, mesangial deposits, mesangial cell volume, and capillary wall deposits during the 8 weeks of daily BGG infusion. However, none of the differences between the groups achieved statistical significance. Changes in mesangial cell volume and capillary wall deposits were also evaluated in study A and study B, but were not found to be different between the enalapril and placebo groups. In both study A and study B, blood pressure was lower in the enalapril groups. In conclusion, in the initial phase of IC-GN induction (0 to 8 weeks), enalapril therapy does not significantly influence the glomerular accumulation of mesangial matrix or immune deposits. However, in established IC-GN (after 8 weeks of GN induction), enalapril therapy significantly decreases the further accumulation of mesangial matrix and may decrease the further accumulation of mesangial deposits. Whether this benefit of enalapril therapy was related to lower blood pressure or to other effects of angiotensin-converting enzyme (ACE) inhibition was not determined in this study.

The development of focal segmental glomerulosclerosis in masugi nephritis is based on progressive podocyte damage

We analysed the sequence of structural changes leading to focal segmental glomerulosclerosis (FSGS) in chronic Masugi nephritis. The protocol resulted in an immediate onset of the disease and the development of segmental sclerosis in a considerable proportion of glomeruli within 28 days of serum injection. Throughout the study, the degree of structural damage was significantly correlated with protein excretion. Even 1 day after injection of the serum, the whole spectrum of early lesions was encountered involving all three cell types. Endothelial detachments, mesangiolysis and podocyte foot process effacement were most prominent. There was focal persistence of capillary microthrombosis but, generally, mesangial and endothelial injuries recovered. The development of podocyte lesions was different: on one hand recovery was seen leading to the re-establishment of an interdigitating foot process pattern, and on the other persistent podocyte detachments from peripheral capillaries allowed the attachment of parietal epithelial cells to "naked" portions of the glomerular basement membrane (GBM), and thus to the formation of a tuft adhesion to Bowman's capsule. Progressive podocyte degeneration at the flanks of an adhesion permitted expansion of the adhesion by encroachment of parietal cells onto the tuft along the denuded GBM. Inside an adhesion, capillaries and mesangial areas either collapse or become obstructed by hyalinosis or thrombosis. Resident cells disappear progressively from inside an adhesion; macrophages may invade. Segmental sclerosis in this model consists of collapsed tuft structures adhering broadly to the cortical interstitium. Proliferation of mesangial cells did not contribute to this development. Recovery of endothelial and mesangial lesions was associated with cell proliferation in early stages of the disease; podocyte proliferation was not encountered at any stage. We conclude that the inability to replace an outmatched podocyte crucially underlies the development of sclerosis. Severe podocyte damage cannot be repaired but leads to tuft adhesions to Bowman's capsule followed by progressive collapse of tuft structures inside an adhesion, resulting in segmental glomerulosclerosis.

Quantitative ultrastructural study of afferent and efferent arterioles in IgA glomerulonephritis and benign nephrosclerosis

Arteriolosclerosis frequently occurs in IgA nephritis (IgAN), and it is the hallmark of benign nephrosclerosis (BNS). The quantitative ultrastructure of juxtaglomerular arterioles is not known in these disorders. We examined afferent and efferent arterioles in renal biopsies from 25 adult patients with IgAN (hypertension at biopsy: 14 patients) and 9 patients with BNS. Six age-matched living renal transplant donors acted as controls. A systematic independent sample of profiles was obtained in thin sections taken at predetermined levels. The thickness of the media (myomedial cells plus the matrix) and the thickness of the medial matrix were estimated stereologically. From these estimates, the matrix/myomedia ratio was calculated. In IgAN with normotension or hypertension, the afferent media and its compartments did not exhibit significant thickening compared with the controls, whereas in BNS the afferent media and its layers were markedly and significantly thickened. The efferent media in IgAN and BNS displayed mild and significant thickening, with significant thickening of the matrix in BNS and IgAN with normotension. The matrix/myomedia ratio was not altered significantly in any group. The results indicate that the afferent arterioles are not the main sites of IgAN-related arteriolosclerosis, that arteriolosclerosis in IgAN and arteriolosclerosis in BNS are different lesions, and that increased efferent arteriolar thickness, demonstrated here for the first time in IgAN and BNS, might be a manifestation of angiotensin II-mediated autoregulatory efferent vasoconstriction exerted to maintain the glomerular filtration pressure.

L-arginine depletion inhibits glomerular nitric oxide synthesis and exacerbates rat nephrotoxic nephritis

Nitric oxide (NO) synthesis is induced in glomeruli in glomerulonephritis; its role in the pathogenesis of glomerular injury is unknown. Interpretation of its role using the currently available analogues of L-arginine as in vivo inhibitors of NO is complicated by their lack of specificity for inducible NO synthase (iNOS). As NO synthesis by iNOS depends on extracellular L-arginine, we have here examined effects of L-arginine depletion on glomerular NO synthesis and the course of accelerated nephrotoxic nephritis (NTN). Arginase, which converts L-arginine to urea and L-ornithine, was used to achieve L-arginine depletion. A single dose of i.v. arginase produced complete depletion of plasma arginine for four hours. Two forms of NTN were induced in preimmunised rats by nephrotoxic globulin: (1) the systemic form of the model by intravenous nephrotoxic globulin; or (2) the unilateral form of model by left kidney perfusion with nephrotoxic globulin, which avoids the complications of systemic administration of nephrotoxic globulin. Arginase reduced plasma arginine levels and the synthesis of nitrite (the stable end-product of NO) by NTN glomeruli (95% inhibition). Proteinuria was exacerbated. There was no effect on early (24 hr) leukocyte infiltration. In the systemic form of the model arginine depletion by i.v. arginase increased glomerular thrombosis at 24 hours, and the severity of histological changes at four days, accompanied by systemic hypertension. In the unilateral form of the model, where i.v. arginase did not induce hypertension, there was no increase in thrombosis or histological severity of nephritis. These results show that arginine depletion, which inhibits glomerular NO synthesis in NTN, leads to increased proteinuria. Where injury is severe, or accompanied by systemic hypertension, the disease is further exacerbated by glomerular thrombosis. These results suggest that NO has an important role in limiting acute glomerular injury.

Glomerular macrophages in nephrotoxic serum nephritis are activated to oxidize low-density lipoprotein

Studies were undertaken to investigate the hypothesis that infiltrating glomerular macrophages in experimental glomerulonephritis are activated to produce oxygen-free radicals that are capable of enhancing oxidation of low-density lipoprotein (LDL). Low-density lipoprotein oxidation was assessed by increased electrophoretic mobility on agarose gel electrophoresis and by the generation of thiobarbituric acid-reactive substances. Lipoprotein uptake, degradation, and re-esterification by macrophages were assessed by measuring 14C-oleic acid incorporation into cholesteryl oleate. Both peritoneal and glomerular macrophages have the ability to oxidize LDL to a form showing increased mobility on agarose gel electrophoresis. However, LDL incubated with glomerular macrophages underwent greater oxidation, resulting in increased generation of thiobarbituric acid-reactive substances (15.1 +/- 1.2 nmol malondialdehyde/mg LDL protein v 7.2 +/- 2.1 nmol malondialdehyde/mg LDL protein; P < 0.01). In addition, glomerular macrophages modified LDL to a form that greatly enhanced cellular synthesis of cholesteryl oleate compared with peritoneal macrophage-modified LDL (30 +/- 11 pmol/10(6) cells/hr v 10 +/- 4 pmol/10(6) cells/hr; P < 0.01). Superoxide dismutase, a scavenger of superoxide anion, inhibited macrophage-mediated oxidation of LDL. These results suggest that glomerular macrophages from nephritic rats are activated to modify LDL to a form avidly taken up by macrophage scavenger receptors. Thus, enhanced formation of oxidized LDL by infiltrating glomerular macrophages may contribute to glomerular injury in nephrotoxic serum nephritis.

Combined antihypertensive and lipid-lowering therapy in experimental glomerulonephritis

We examined the interrelation between systemic hypertension, hyperlipidemia, and progressive renal injury in experimental glomerulonephritis. Induction of nephrotoxic serum nephritis in Sprague-Dawley rats led to systemic hypertension and hyperlipidemia. Four groups of rats were studied over a 16-week period: (1) untreated nephritic rats; (2) nephritic rats treated with hydralazine, reserpine, and lasix (AH); (3) nephritic rats treated with lovastatin (4 mg/kg) (Lova); and (4) nephritic rats treated with combined antihypertensive/lipid-lowering therapy (AH/Lova). Systolic blood pressure rose progressively in untreated rats (152 +/- 4 mm Hg at 16 weeks). Blood pressure was reduced by antihypertensive therapy (P < .001) (108 +/- 2 mm Hg in the AH group and 111 +/- 3 mm Hg in the AH/Lova group) but remained elevated in animals treated with lovastatin alone (P > .05) (156 +/- 3 mm Hg in the Lova group). Serum cholesterol rose progressively in untreated rats (3.70 +/- 0.85 mmol/L [143 +/- 33 mg/dL] at 16 weeks). The rise in serum cholesterol was prevented by lovastatin therapy (P < .001) (2.22 +/- 0.41 mmol/L [86 +/- 16 mg/dL] in the Lova group and 2.09 +/- 0.52 mmol/L [81 +/- 2 mg/dL] in the AH/Lova group) but not antihypertensive therapy (P > .05) (2.92 +/- 0.65 mmol/L [113 +/- 25 mg/dL] in the AH group). Proteinuria was reduced by antihypertensive therapy (P < .001) and lipid-lowering therapy (P < .05) (16-week values: 1.069 +/- 0.167 g/d in untreated rats, 0.663 +/- 0.164 g/d in the Lova group, 0.392 +/- 0.051 g/d in the AH group, and 0.176 +/- 0.035 g/d in the AH/Lova group).(ABSTRACT TRUNCATED AT 250 WORDS)

Nephron underdosing: a programmed cause of chronic renal allograft failure

The findings cited in this report suggest that renal allograft survival might be improved by matching nephron supply to recipient needs (analogous to prescription dialysis based on Kt/V). Methods for assessing functional graft capacity (ie, nephron number, filtration, or total microvascular surface area) are needed. Graft weights might serve as a useful alternative until better indices are devised. Measures for defining and possibly reducing recipient demands are also needed to preserve graft performance. Where gross imbalances between nephron supply and recipient demand are not likely to be corrected over the long term by engraftment of a single kidney, consideration should be given to dual kidney transplantation, currently feasible only from cadaveric, but eventually from xenogeneic sources as well. The predicted longer survival and avoidance of premature return to end-stage renal disease with the transplantation of two kidneys in certain conditions could render this approach more rational, both in clinical and economic terms, than single kidney engraftment for those at greatest risk for shortened graft survival. The dosing of larger numbers of nephrons might also lessen the risk of coexistent hypertension and thereby reduce the magnitude and tempo of immune injury to the graft.

Hypertension and renal disease

Chronic renal parenchymal disease is the most common cause of secondary hypertension: By the time end-stage renal disease develops, its prevalence approaches 75-85%. It was previously believed that hypertension caused arteriolar nephrosclerosis and ischemic renal injury superimposed on primary renal parenchymal disease, contributing to progressive renal insufficiency. Recently, the importance of an increased intraglomerular hydraulic pressure due to loss of renal autoregulation has been emphasized. There are several potential explanations concerning clinical studies which have not uniformly demonstrated slowing of progressive renal damage with antihypertensive therapy: Random BP measurements may not adequately reflect average BP levels, or, alternatively, the widely accepted target level of BP control may be inadequate. In a retrospective study, we found that hypertensive nephropathics had higher serum creatinine levels than normotensives; in another prospective trial we have demonstrated that enalapril is an effective antihypertensive agent in patients with IgA nephropathy, and it also ameliorates the evolution of the disease.

Renal extraglomerular vascular immune deposits in IgA glomerulonephritis

Kidney biopsies of 425 patients with IgA glomerulonephritis were studied to reveal the incidence, composition and possible clinical significance of extraglomerular vascular immune deposits. IgA deposits were detected in 20 cases, IgM in 28 (in 5 together with IgA), C3 in 317 and no vascular deposits in 60 cases. C3 and IgA deposits were granular, resembling mesangial deposits, while IgM deposits were lumpy, similar to IgM deposits in sclerotic and hyalinized glomeruli. The incidence of vascular lesions in patients with IgA (30%) and C3 deposits (24%) was not significantly higher as compared to those without vascular deposits (20%), but was significantly higher in patients with IgM deposits (68%, P < 0.00004). Only the presence of vascular IgM deposits correlated significantly with severe glomerulosclerosis, arterial hypertension and elevated serum creatinine levels (all P < 0.001). We conclude that neither C3 nor IgA deposits, in spite of their suggested immune complex nature, contribute significantly to the development of vascular lesions. Lumpy IgM deposits, probably the result of insudation of plasma proteins into the blood vessel walls, were associated with advanced vascular lesions and glomerulosclerosis and are probably a part of non-immune mediated progression of IgA glomerulonephritis.

Dietary protein restriction and glomerular permselectivity in nephrotoxic serum nephritis

We have previously demonstrated that long-term dietary protein restriction ameliorates proteinuria and limits glomerular structural injury in rats with nephrotoxic serum nephritis. In the present study, we examined the influence of short-term dietary protein restriction on glomerular permselectivity. As compared to nephritic rats maintained on a normal protein diet, whole kidney and single nephron hemodynamics were lower in nephritic rats subjected to dietary protein restriction of three days duration (glomerular filtration rate: 0.79 +/- 0.10 vs. 1.46 +/- 0.11 ml/min, P less than 0.003; renal plasma flow rate: 2.50 +/- 0.34 vs. 3.96 +/- 0.38 ml/min, P less than 0.02; glomerular capillary pressure: 44 +/- 1 vs. 53 +/- 1 mm Hg, P less than 0.002; proteinuria: 77 +/- 15 vs. 224 +/- 14 mg/24 hr, P less than 0.01). This was associated with a rise in afferent resistance, from 2.99 +/- 0.77 to 5.45 +/- 0.94 dyn.sec.cm-5, NS. In nephritic rats maintained on 24% protein, fractional clearances were elevated above control values for neutral dextrans with molecular radii exceeding 50 A but were depressed for those with molecular radii below 30 A (P less than 0.05). Dietary protein restriction elevated the fractional clearances of dextrans with radii less than 30 A while depressing the fractional clearances of dextrans with radii greater than 50 A (P less than 0.05). The proportion of glomerular filtrate permeating the shunt pathway was elevated above control values in nephritic rats on the 24% protein diet but declined in those fed the low protein diet (NSN-24%: 0.86%; NSN-6%: 0.31%; control: 0.19%).(ABSTRACT TRUNCATED AT 250 WORDS)

Glomerular hypertrophy in minimal change disease predicts subsequent progression to focal glomerular sclerosis

The study sought a diagnostic clue to identify the group of pediatric patients with apparent minimal change disease who subsequently develop focal glomerular sclerosis (FGS). Review of all renal biopsy material at our institutions identified 42 pediatric patients who met the standard criteria for minimal change disease (MCD) on initial biopsies. Of those, 10 deteriorated clinically and on rebiopsy showed focal glomerular sclerosis (FGS). The initial renal biopsies of these 10 patients were analyzed morphometrically to determine the mean glomerular tuft area (GA). The results were compared to those of the remaining 32 patients whose subsequent benign clinical course was consistent with MCD, and to randomly selected, age-matched autopsy controls without renal disease (CONT, N = 10). The mean age was comparable among the three groups studied. Separate groups of adult (N = 12) and pediatric (N = 18) patients with initial biopsies with FGS were also studied. The initial biopsy of pediatric patients who subsequently showed FGS (rebiopsy performed on average 3.3 years later) had an average GA of 13.5 x 10(-3) mm2, 76% larger than glomeruli from children with MCD (7.7 x 10(-3) mm2, P less than 0.0005) and 62% larger than CONT (8.4 x 10(-3) mm2, P less than 0.005). Patients with FGS on initial biopsy, whether adult or pediatric, also had significantly larger GA than the age-matched MCD or CONT groups. Evaluation of GA in all the 42 pediatric biopsies with initial MCD further showed that in 23 patients GA was equal to or smaller than the CONT average.(ABSTRACT TRUNCATED AT 250 WORDS)

Microvascular disease and the progression of IgA nephropathy

In order to examine the role of microvascular disease in the evolution of IgA nephropathy (IgAN), the interrelationships among vascular sclerosis, glomerular sclerosis, age, and hypertension were determined by morphometric analysis of renal biopsies in 71 patients with IgAN; 63 age- and sex-matched individuals with minimal change nephrotic syndrome (MCNS) served as normal controls. The following parameters in glomeruli and in vessels with an outer diameter of 60 microns or less were analyzed by multiple regression analysis: (1) percentage of glomeruli with segmental and/or global sclerosis; (2) percentage of vessel area in renal cortical tissue measured by the point-counting method; (3) index of hyaline change estimated as the percentage of the number of arteries showing hyaline change; (4) index of vessel wall thickness determined by the ratio of mural thickness to outer diameter of arteries; (5) number of vascular cross sections counted per 6.25 microns2. The results of the multiple regression analysis demonstrate that glomerular and vascular sclerosis are interrelated and that hypertension and vessel area are almost equally important as predictors of glomerular sclerosis. Vessel area proved to be an early marker of vasculopathy, as its values in IgAN, even in the absence of hypertension and/or glomerular sclerosis, exceeded those in age- and sex-matched controls (with MCNS). These data, obtained by the use of quantitative methods, establish a role for vessel disease and hypertension in the progression of IgAN.

Role of iron in the tubulo-interstitial injury in nephrotoxic serum nephritis

We studied the possibility that tubule fluid iron could be involved in the pathogenesis of the tubulo-interstitial injury associated with primary glomerular disease. Tubule fluid iron is determined by the magnitude of the glomerular leak for transferrin and the iron saturation of transferrin. To minimize tubule fluid iron in an experimental model of glomerulonephritis, iron deficiency was induced in rats prior to the induction of nephrotoxic serum nephritis. Iron deficiency did not effect the development of glomerular disease as determined by proteinuria, but had a marked effect on preventing the development of tubulo-interstitial disease and renal functional deterioration. There was also a strong correlation between the amount of functional deterioration and extent of tubulo-interstitial disease and urinary iron excretion in both the control and iron deficient animals. It is proposed that injury results from iron being dissociated from transferrin at the more acid pH of the tubule fluid. Iron, a transition element, is able to catalyze the Haber-Weiss reaction with the formation of free hydroxyl radicals which causes renal tubule cell injury. This tubulo-interstitial injury is the major determinate of progressive renal functional deterioration in this experimental model of glomerulonephritis.

Renal injury in DOCA-salt hypertensive C5-sufficient and C5-deficient mice

We induced hypertension by uninephrectomy and treatment with desoxycorticosterone (DOCA) and 1% NaCl in the drinking water in congenic mice that differ in the single gene locus responsible for the presence or absence of the complement component C5 and compared them to uninephrectomized normotensive (no DOCA-NaCl) mice. In contrast to C5-sufficient (C5S) mice. C5-deficient (C5D) mice can neither generate C5a nor assemble C5b-9. After four weeks of treatment, DOCA-C5S and -C5D mice developed similar degrees of hypertension; mice receiving no DOCA remained normotensive. Only hypertensive mice developed glomerular injury. Hypertensive DOCA-C5D mice developed more glomerular capillary loop dilatation and larger glomerular capillary tuft volumes than DOCA-C5S mice (1.0 +/- 0.1 vs. 0.7 +/- 0.03 X 10(6) microns 3, respectively, P less than 0.05). However, DOCA-C5S mice, compared to DOCA-C5D mice, had significantly more glomerular cell proliferation (64.5 +/- 2 vs. 42 +/- 3 nuclei/glomerulus), cell necrosis (injury score 22 +/- 1 vs. 17 +/- 1), extracapillary proliferation (26 +/- 4 vs. 2.5 +/- 2% of glomeruli) and proteinuria (5.9 +/- 0.8 vs. 3.7 +/- 0.5 mg/24 hr; all P less than 0.05). By immunofluorescence microscopy both DOCA-C5S and -C5D had mesangial C3 deposits but only DOCA-C5S mice had C9 deposits. After 16 weeks of DOCA-NaCl C5S mice, in comparison to C5D mice, had more severe glomerulosclerosis (injury score 50 +/- 6 vs. 12 +/- 4), proteinuria (16.6 +/- 0.1 vs. 9 +/- 0.1 mg/24 hr), and renal insufficiency (serum creatinine 0.25 vs. 0.15 mg/dl), all P less than 0.05. These changes occurred despite levels of hypertension that were similar in DOCA-NaCl C5S and C5D throughout the whole study period. We conclude that C5a and/or C5b-9 may play an important role in hypertensive glomerular injury. Moreover, these studies demonstrate that differences in host responses may determine target organ susceptibility to similar injurious mechanisms.

Effect of indomethacin on glomerular permselectivity and hemodynamics in nephrotoxic serum nephritis

The present study was undertaken to determine the effects of prostaglandin synthesis inhibition on glomerular hemodynamics in nephrotoxic serum nephritis and to elucidate the mechanisms by which prostaglandin synthesis inhibition reduces proteinuria in nephritic rats. Dextran sieving studies were performed before and after intravenous administration of indomethacin to control rats and to nephritic rats with heavy proteinuria. Indomethacin did not significantly alter mean arterial pressure, glomerular filtration rate or proteinuria in control rats nor were significant changes in dextran sieving observed. By contrast, in nephritic rats indomethacin significantly reduced glomerular filtration rate (2.58 +/- 0.50 vs. 1.39 +/- 0.27 ml/min, P less than 0.001), proteinuria (0.198 +/- 0.079 vs. 0.048 +/- 0.019 mg/min, P less than 0.05) and filtration rate-corrected proteinuria (0.059 +/- 0.033 vs. 0.031 +/- 0.013 mg/ml GFR, P less than 0.05). The fractional clearance of neutral dextrans with molecular radii exceeding 42 A were elevated above control values in nephritic rats (P less than 0.05). After administration of indomethacin, the fractional clearance of neutral dextrans uniformly declined toward control values and remained elevated only for molecular radii exceeding 54 A. Assessment of glomerular hemodynamics in nephritic rats before and after indomethacin showed significant declines in single nephron filtration rate (31.5 +/- 3.0 vs. 21.2 +/- 2.5 nl/min, P less than 0.02), glomerular plasma flow rate (99.5 +/- 6.7 vs. 68.5 +/- 7.8 nl/min, P less than 0.05) and glomerular ultrafiltration coefficient (0.0430 +/- 0.0033 vs. 0.0339 +/- 0.0032 nl.sec-1.mm Hg-1, p less than 0.05). Indomethacin did not significantly change these parameters in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenesis and significance of nonprimary focal and segmental glomerulosclerosis

Injury of the glomerular microvasculature by nonimmunologic processes is often the underlying mechanism of progressive deterioration of renal function in patients with a variety of renal disorders. The structural hallmark of this injury is focal and segmental glomerulosclerosis, often accompanied by entrapment of hyalin. Although such lesions are quite characteristic for diseases that primarily affect the glomerular podocyte, similar damage occurs in association with functional and structural adaptive changes that develop as a consequence of a significant loss of functioning nephrons or other systemic disorders. Experimental studies have revealed that such functional adaptations include intrarenal vasodilatation that through increases in glomerular capillary pressure and plasma flow leads to a significant compensatory hyperfiltration. This functional state is accompanied by a parallel increase in glomerular volume, attained chiefly by expansion of matrix components and an increase in the number of endothelial and mesangial cells, but not of podocytes. The persistence of the adaptive changes results in endothelial, mesangial, and epithelial cell dysfunction revealed clinically by proteinuria and structurally by the development of microthrombosis, microaneurysms, mesangial expansion, and occlusion of capillaries by hyalin accumulation. Although all these pathologic processes can lead to segmental collapse of the capillary tuft, it is the progressive hyalin deposition in capillaries with defective or detached podocytes that represents the major mechanism in the development of segmental and eventually global glomerulosclerosis. The inability of the highly differentiated podocyte to replicate in response to systemic or locally released trophic factors ultimately results in imperfections of the capillary wall that set the stage for permeability defects amplified and accentuated by greatly augmented hydrodynamic forces. These structural and functional microvascular changes acting in concert not only facilitate the transcapillary convection of macromolecules that results in albuminuria, but can also be anticipated to play a key role in the entrapment and accumulation of larger macromolecules in front of the lamina densa in the form of hyalin material. Continuing damage to the glomerular microvasculature exacerbates the adaptive changes in surviving nephrons, closing a positive-feedback loop that culminates in end-stage renal failure.

The role of adaptation in allograft acceptance

The experimental and clinical data suggest that both a decrease of antigen expression and decreased perfusion can protect against immunologically mediated destructive processes. In the adaptation of skin grafts, these factors could be interrelated. Inadequate perfusion might lead to a decreased delivery of substances that stimulate MHC antigen expression. This course of events also could explain the protection in the patient presented here. Immune deposits were completely absent in the protected segment of the kidney, although immune deposits were abundantly present in the remaining part of the kidney, and circulating anti-donor antibodies were demonstrable after the transplanted kidney had been removed. The limited availability of frozen biopsy material has prevented us from comparing the expression of MHC antigens in both kidney segments using monoclonal antibodies. But such studies might be done in experimental kidney transplants with an artificially induced stenosis of the renal artery. Except when an arterial stenosis is present, we have little reason to assume that perfusion gradually decreases in longstanding kidney grafts as it does in skin grafts. Therefore, if adaptation plays a role in the gradual decrease of the sensitivity to rejection in longstanding kidney grafts, this phenomenon must be attributed to a decreased expression of target antigens as a consequence of factors other than decreased perfusion. The most likely candidates are the immunosuppressive drugs, such as cyclosporine and prednisone, which decrease MHC antigen expression. Let me conclude by returning to my main theme of graft adaptation. It seems appropriate to end this review with a quotation from one of Woodruff's original publications on this subject: "If the phenomenon [adaptation] applies to homotransplants of normal tissues to sites other than the eye, I think it almost certain that the clinical homograft problem will be solved; if it does not, the problem may prove insoluble" [9]. Although our insight into the rejection process has increased considerably, we still do not know which factors are most important in determining the long-term survival of primarily vascularized grafts.

Role of coagulation in glomerular injury

A role for coagulation in renal diseases is suggested by the presence of glomerular fibrin deposits in numerous experimental and human renal diseases, some of which are of toxic origin. Fibrin may exert detrimental effects by occluding glomerular capillaries, by attracting macrophages or by direct cytotoxicity to mesangial cells. Intraglomerular fibrin deposition or formation may result in part from changes in the normal multiple haemostatic properties of glomeruli. In glomerular clotting of systemic origin, e.g., glycerol-induced acute renal failure with intravascular coagulation, inhibition by drugs of glomerular fibrinolytic activity leads to persistent thrombi and permanent renal damage. In immune glomerulonephritis, fibrin formation may depend on activation of glomerular prothrombotic properties: for example, glomerular procoagulant (tissue factor-like) activity is enhanced at the peak of mercuric chloride-induced autoimmune glomerulonephritis, characterized by massive fibrin deposits. Finally, fibrin deposits probably contribute to the progressive renal lesions and chronic renal failure seen in rats with kidney damage, in which anticoagulant therapy has a beneficial effect.

Progression of renal insufficiency: role of blood pressure

The effect of blood pressure on progression of renal insufficiency was examined in a large group of patients who eventually required dialysis. Out of 198 consecutive new chronic dialysis patients, 86 had sufficient data predialysis to determine rates of progression of renal insufficiency by reciprocal creatinine versus time plots. Average plasma creatinine at first contact was 3.8 +/- 0.2 mg/dl and at the time of dialysis was 11.4 +/- 0.4 mg/dl. Mean duration of follow-up was 33.4 +/- 2.5 months and the average rate of decline in reciprocal creatinine was -0.009 +/- 0.001 dl/mg month. Patients were stratified by average value of diastolic blood pressure measured in clinic. Patients in the lowest quartile had a rate of decline in reciprocal creatinine of -0.007 +/- 0.001 dl/mg month, which was slower than that of patients in the third and fourth quartiles, -0.010 +/- 0.001 and -0.011 +/- -0.002 dl/mg month, respectively (P less than 0.05). In individual patients, a mean diastolic BP of less than 90 mm Hg was associated with a rate of decline in reciprocal creatinine of -0.006 +/- 0.001 dl/mg month which was significantly less than the rate of -0.009 +/- 0.001 when the diastolic BP was greater than 90 mm Hg. Thus, in a large group of patients who have progressed to ESRD, there is an association between control of diastolic blood pressure and a slower rate of decline in renal function.

Glomerular hemodynamic changes vs. hypertrophy in experimental glomerular sclerosis

In a variety of recent studies in animals with chronic renal diseases, investigators have found a tight correlation between the elevation in glomerular pressures and flows versus glomerular hypertrophy. To investigate a possible causal link between the glomerular hyperfunction and hypertrophy, we studied the functional and morphological sequelae of nephrectomy and those of unilateral ureteral diversion (UD) into the peritoneal cavity (that is, removal of renal clearance function while keeping the kidney tissue in situ). In all nine experimental groups of 54 Munich-Wistar rats, 2/3 of the renal mass was removed from the left kidney by ligation of two or three branches of the left renal artery. In addition, right nephrectomy (NPX) was performed in Groups 1B, 2B and 3B or UD in Groups 1C, 2C and 3C. The right kidney was left untouched in control groups, Groups 1A, 2A and 3A. Micropuncture measurements and histological studies were performed at four days (Groups 1A, 1B and 1C), two weeks (Groups 2A, 2B and 2C) or four weeks (Groups 3A, 3B and 3C). At both four days and two weeks, NPX and UD groups had marked and comparable degrees of glomerular hypertension, hyperperfusion and hyperfiltration compared to the control group in the left kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

[Loss of renal functional reserve following kidney transplantation and in patients with advanced disorders of liver function]

Renal functional reserve capacity was evaluated in healthy controls, kidney transplant recipients and patients with impaired liver function by simultaneous measurements of periodic clearances of inulin, PAH and creatinine every 30 minutes before, during and after infusion of an amino acid (AA) solution. During AA infusion glomerular filtration rate rose in 10 healthy controls to about 35% above basal values (inulin clearance from 107 +/- 6 to 144 +/- 7 ml/min, p less than or equal to 0.0005), renal plasma flow increased by 27% (PAH clearance from 530 +/- 25 to 675 +/- 40 ml/min, p less than or equal to 0.002). 8 renal transplant recipients with good and stable renal function (creatinine clearance above 65 ml/min) showed no rise in GFR and RPF, as did 10 patients with severe impairment of liver function and normal basal kidney function (creatinine clearance above 100 ml/min). The lack of renal functional reserve in kidney transplant recipients might indicate a hyperfiltration of the transplanted kidney. This could affect the longtime prognosis of these patients. The liver seems to play a role in the mediation of the amino acid-induced rise of GFR, supporting the hypothesis of a putative liver hormone regulating GFR after protein ingestion or AA infusion.

Glomerular size-selective barrier dysfunction in nephrotoxic serum nephritis

We have previously reported amelioration of heavy proteinuria, vascular sclerosis and glomerular structural damage by antihypertensive therapy in nephrotoxic serum nephritis (NSN). In the present study, we examine glomerular permselectivity in this hypertensive form of NSN and the effect of hypertension treatment on size-selective barrier function. Mean arterial pressure was maintained at normotensive levels (mean 123 +/- 3 mm Hg) with a combination of hydralazine, hydrochlorthiazide and reserpine in 7 nephritic rats, while 10 untreated rats remained hypertensive (mean 165 +/- 4 mm Hg). At six weeks, glomerular filtration rate was reduced in untreated rats (mean 0.54 ml/min) but was preserved in those rendered normotensive (mean 1.71 ml/min), P less than 0.02). Twenty-four-hour urinary protein excretion, mean 371 +/- 74 mg in hypertensive nephritic rats, was markedly reduced in rats on the antihypertensive regimen to a mean of 120 +/- 17 mg (P less than 0.02), as was 24-hour urinary gamma-globulin excretion (mean 35 +/- 9 mg in untreated vs. 16 +/- 2 mg in treated). Fractional clearances of tritiated polydisperse neutral dextrans were significantly enhanced for molecular radii exceeding 50 angstroms in hypertensive animals, indicative of a loss of glomerular size permselectivity. Rats on antihypertensive therapy did not develop such a size selective defect. Thus, hypertensive rats with nephrotoxic serum nephritis develop "gaps" in the glomerular basement membrane which allow the excretion of large molecular weight neutral dextrans and gamma-globulin. This defect in glomerular permselectivity can be averted with antihypertensive therapy.

Focal and segmental glomerulosclerosis: analogies to atherosclerosis

In summary, both the developing atherosclerotic and FSGS lesions seem to share certain postulated pathophysiologic mechanisms, including endothelial cell injury, macrophage infiltration, hyperlipoproteinemia, and hypertension. As depicted in Figure 1, any initial glomerular injury results in flux of macromolecular substances into the glomerular mesangium. As an adjunct to increased glomerular barrier dysfunction, hyperlipoproteinemia is believed to secondarily develop from the dramatic losses of albumin, stimulating increased hepatic lipoprotein synthesis and the loss of lipoprotein lipase-activating substance into the urine which would effectively produce a reduction in circulating chylomicra and triglyceride catabolism. Certain elevated circulating lipoproteins could, theoretically, pass through the damaged glomerular filter into the mesangium, thereby enhancing the flux of macromolecules. Also associated with certain experimental glomerular disorders is the development of glomerular hypertension, as manifested by an elevated glomerular capillary hydrostatic pressure (PGC), which can further augment macromolecular flux into the mesangium. Overloading of the glomerular mesangium by the above mechanisms is believed to be an injurious stimulus for MC to both proliferate and produce excess mesangial matrix substance. Both of these events are thought to be pathologic harbingers of glomerulosclerosis. Glomerular hypertension is also capable of damaging endothelial cells within the glomerular microcirculation, and this purportedly can activate platelets and result in glomerular thrombosis. At present, it is unclear how glomerular thrombosis produces increased mesangial cell injury; however, this process is believed to cause both systemic and glomerular hypertension which may serve as intermediary mechanisms producing the untoward effects of mesangial cell proliferation and matrix overproduction.

Nephrotoxic serum nephritis with hypertension: perfusion pressure and permselectivity

We examined the effect of acute reduction in renal perfusion pressure on proteinuria and glomerular permselectivity in a model of nephrotoxic serum nephritis which is characterized by hypertension, heavy proteinuria and severe structural injury. Sequential dextran sieving studies were performed after two weeks of nephritis in 10 uninephrectomized rats at their basal elevated blood pressure levels (154 +/- 3 mm Hg) and at lowered renal perfusion pressure of 105 to 110 mm Hg, achieved by adjusting a ligature around the aorta above the origin of the renal artery. Glomerular filtration rate (GFR) decreased from 1.35 +/- 0.24 to 0.95 +/- 0.19 ml/min (P less than 0.002), while urinary protein excretion (factored for filtration rate) declined from 0.69 +/- 0.2 to 0.39 +/- 0.1 mg per ml GFR (P less than 0.002) at the lower perfusion pressure. A companion protocol documented a modest reduction in renal plasma flow (RPF) from 4.96 +/- 0.48 to 4.44 +/- 0.63 ml/min (P less than 0.05) and a decline in glomerular transcapillary hydraulic pressure difference (delta P) from 43 to 33 mm Hg (P less than 0.001) during the ligature maneuver. In the hypertensive state, fractional clearances of neutral dextrans (theta ND) with molecular radii exceeding 40 A were elevated in nephritic rats as compared to uninephrectomized non-nephritic controls. With reduction in renal perfusion pressure. Theta ND uniformly declined toward control values and remained significantly elevated only for molecular radii exceeding 55 A. The calculated fraction of glomerular filtrate passing through a non-size discriminatory shunt, pathway was 0.93% during the hypertensive period and was reduced at lower perfusion pressures to 0.52% (to be compared to 0.19% in controls).(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenesis of systemic hypertension and glomerular injury in the spontaneously hypertensive rat

Weanling and young spontaneously hypertensive rats (SHRs) demonstrate higher plasma renin activity and plasma aldosterone concentration than age-matched normotensive Wistar-Kyoto (WKY) control rats. In addition, this age group exhibits a salt-retaining tendency not seen in WKYs. Nevertheless, when they reach adulthood, these differences between SHRs and WKYs are all but abolished, yet hypertension persists in SHRs. The possible mechanisms leading to these changes in SHRs and to the differences seen with advancing age are discussed. Results of micropuncture studies that help elucidate the glomerular hemodynamic adaptations to elevation in systemic blood pressure in young SHRs are also presented. Evidence is advanced suggesting that increased intraglomerular pressure is responsible for the histologic lesions characteristic of untreated severe hypertension. The salutary effects of treatment with vasodilator drugs that reduce intraglomerular pressure are emphasized.

The influence of concomitant experimental hypertension and glomerulonephritis

Utilizing the two kidney-one clip Goldblatt model (CH), we have examined the influence of hypertension upon the course of antiglomerular basement membrane antibody-induced glomerulonephritis (GN) over a period of 10 to 14 weeks after induction of CH and GN, utilizing evaluations in the awake rat by renal micropuncture of the unclipped kidney and morphologic analysis (control [C], GN, CH, and GN+CH). Metabolic studies revealed that GN and GN+CH rats developed proteinuria, elevations in serum creatinine and blood pressure (P less than 0.05). GN+CH resulted in significant reductions in two kidney glomerular filtration rate (GFR) below values in C, and GFR in the unclipped kidney was markedly reduced when compared to CH. The glomerular capillary hydrostatic pressure and the pressure gradient( (delta P) were elevated approximately 4 to 5 mm Hg in GN and CH rats and 6 mm Hg above GN and CH values in the GN+CH rats. The glomerular ultrafiltration coefficient (LpA) was reduced to approximately 40% of C in both GN and GN+CH in spite of further increases in delta P. Surface nephron filtration rate was similar in all groups, suggesting glomerular dysfunction was primarily in nephrons below the surface in GN+CH. Morphologic evaluation revealed that GN+CH exhibited a combination of diffuse and focally sclerotic lesions characteristic of GN and CH, respectively. Documented further increases in PG did not worsen glomerular morphology, but kidney GFR did decrease. Hypertension induced deterioration of glomerular function in nephrons below the surface was not associated with marked morphologic deterioration, but a combination of the characteristics of GN and CH.

Hypertension and renal diseases

Experimental data are summarized that provide evidence that enhanced transmission of systemic hypertension to the glomerulus occurs in the setting of reduced renal mass. It is proposed that similar adaptive glomerular hemodynamic alterations occur in parenchymal renal disease in humans, favoring the development of intraorgan hypertension. Accelerated vascular and glomerular damage and functional deterioration result. Treatment of systemic hypertension with agents that reduce glomerular capillary pressure has been shown to ameliorate the manifestations of experimental glomerular disease. The importance of preventing hemodynamic injury to the arterioles and glomerular capillaries in the management of human renal disease is stressed.

The effect of hypertension on glomerular structures and capillary permeability in passive Heymann glomerulonephritis

In glomerulonephritic and normal kidneys hypertension has been shown to increase the urinary protein excretion and the thickness of the glomerular basement membrane and to reduce the glomerular filtration rate. We have studied the effect of desoxycorticosterone acetate (DOCA)-salt hypertension on the glomerular anatomy and function in normal control rats and rats with passive Heymann nephritis. Standard methods for measurements of glomerular filtration rate and urinary protein excretion were used and the results were correlated to morphometrical measurements in randomly selected glomeruli in all groups. In control rats, DOCA-salt hypertension increased the kidney weight (P less than 0.001), the glomerular volume (P less than 0.05), and the surface of peripheral glomerular basement membrane (P less than 0.01). The thickness of peripheral glomerular basement membrane and the length of glomerulary capillaries were not affected. In glomerulonephritic rats, DOCA-salt hypertension did not change the kidney weight and glomerular capillary diameter. The thickness of the peripheral basement membrane increased (P less than 0.05), while the length of glomerular capillaries and the surface of peripheral basement membrane were reduced (P less than 0.05). Glomerular filtration rate per unit peripheral basement membrane was not significantly different among the groups while protein excretion per unit peripheral basement membrane increased significantly both in the hypertensive and in the glomerulonephritic groups. The estimated hydraulic conductivity of the glomerular capillaries was reduced both in rats with DOCA-salt hypertension and glomerulonephritic rats with and without DOCA-salt hypertension. In conclusion, DOCA-salt hypertension seems to decrease hydraulic conductivity and increase protein excretion both in normal and in glomerulonephritic kidneys although the effect on glomerular morphology is different.

Intrarenal hemodynamic alterations induced by anti-GBM antibody

An isolated perfused kidney system (IPK) was used to study the direct intrarenal hemodynamic effects of binding of anti-glomerular-basement membrane (anti-GBM) antibody in the absence of all other circulating humoral and cellular inflammatory mediators. Control IPK's (perfused with Krebs-Henseleit buffered 5% albumin solution containing non-immune globulin) had a renal vascular resistance (RVR) mean +/- SEM 3.10 +/- 0.47 mm Hg/ml/min and a GFR mean +/- SEM 0.63 +/- 0.8 ml/min/g. Anti-GBM antibody administration raised RVR (4.83 +/- 0.52 mm Hg/ml/min, P less than 0.01) and lowered GFR (0.34 +/- 0.04 ml/min/g, P less than 0.01). Perfusate renin activity was higher after antibody administration (684 +/- 87 ng AI/ml/hr compared with control 308 +/- 42 ngAI/ml/hr, P less than 0.01). Treatment with Sar1Ala8All (3 X 10(-6) M) or captopril (10 mg/ml) attenuated antibody-induced vasoconstriction (RVR mm Hg/ml/min, Sara1Ala8All = 3.78 +/- 0.13 captopril = 3.26 +/- 0.12, both P less than 0.05 compared with anti-GBM alone). Both inhibitors of the renin-angiotensin system (RAS) also aggrevated the decline in GFR seen after antibody administration (GFR ml/min/g, Sara1Ala8All = 0.24 +/- 0.05, Captopril = 0.18 +/- 0.03, both P less than 0.05 compared with anti-GBM alone). These IPK studies demonstrate that anti-GBM antibody itself may directly induce intrarenal hemodynamic alterations in the absence of complement activation, neutrophil infiltration, neural influences or circulating vasoactive substances. The results from perfusate renin sampling and blockade of the RAS provide evidence that anti-GBM antibody deposition activates the intrarenal RAS and thereby induces significant hemodynamic alterations.

Glomerular injury in uninephrectomized spontaneously hypertensive rats. A consequence of glomerular capillary hypertension

Micropuncture and/or morphologic studies were performed in intact Wistar-Kyoto rats (WKY) (group 0), intact spontaneously hypertensive rats (SHR) (groups 1 and 5), uninephrectomized (UNX) WKY (groups 2 and 6), and UNX SHR (groups 3 and 4, 7 and 8). UNX was performed when rats were 5 wk of age. Groups 0-4 were observed for 34 wk after which whole kidney clearance and morphologic studies were performed. Groups 5-8 underwent micropuncture study at 10 wk of age. Groups 4 and 8 were fed a diet containing 6% protein. All other rats ingested standard laboratory diet. 5 wk after UNX, normotensive group 6 had higher single nephron glomerular filtration rate (SNGFR) and initial glomerular plasma flow rate (QA) than intact, hypertensive group 5. Glomerular transcapillary hydraulic pressure difference (delta P) was similar in these two groups. Hypertensive group 7 exhibited less elevation in SNGFR and QA than group 6, but delta P was significantly increased. The presence of glomerular capillary hypertension in UNX SHR at 10 wk was associated with the development of significant proteinuria and an increased incidence of mesangial expansion and glomerular sclerosis at 7 mo (group 3) as compared with groups 0, 1, and 2. Protein restriction prevented the development of increased delta P in UNX SHR (group 8) and also conferred long-term protection from increased urinary protein excretion and glomerular injury (group 4). These studies suggest that glomerular capillary hypertension predisposes to glomerular injury in this model of hypertension with reduced renal mass.

Tubuloglomerular feedback and glomerular morphology in Goldblatt hypertensive rats on varying protein diets

The present experiments were performed to examine the effect of variation in protein intake on renal function and morphology in the non-clipped kidneys of Goldblatt hypertensive rats. After renal artery clipping, rats were put on diets containing 5 (LP), 17.5 (NP), or 51% (HP) protein. After 4 to 5 weeks, all rats had developed hypertension. GFR was directly correlated with protein intake (1.47 +/- 0.15 in HP, 1.19 +/- 0.14 in NP, and 0.93 +/- 0.08 ml/min in LP), as was SNGFR (44.2 +/- 1.89, 39.1 +/- 2.23, and 27.9 +/- 0.86 nl/min in HP, NP, and LP rats). The response of SNGFR to changes in loop of Henle flow rate was attenuated in NP and HP rats: the maximum decrease was reduced (30.0 +/- 5.2% in NP, 22.1 +/- 4.2% in HP) and higher tubular flow rates were required to elicit responses (V1/2, the flow rate at which the response is half-maximum, was 28.9 +/- 2.6 nl/min in NP and 28.2 +/- 1.4 nl/min in HP). In LP rats, the maximum response was a decrease of 47.7 +/- 2.5%, and V1/2 was 18.1 +/- 1.2 nl/min, values similar to those found in normal control rats. The weights of the non-clipped kidneys were 0.96 +/- 0.04 g (LP), 1.06 +/- 0.05 g (NP), and 1.36 +/- 0.06 g (HP). In the LP rats there was no difference between the non-clipped and clipped kidneys. Light microscopic evaluation showed a high incidence of focal glomerulosclerosis in non-clipped kidneys of HP rats, but no glomerular lesions in the non-clipped kidneys of LP rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Converting enzyme inhibitor therapy limits progressive glomerular injury in rats with renal insufficiency

Sustained increases in glomerular capillary pressure and flow accompany systemic hypertension in rats that have undergone extensive ablation of the renal mass. These intrarenal hemodynamic changes are, in turn, associated with the progressive development of proteinuria and glomerular sclerosis, leading ultimately to failure of remnant nephron units. The efficacy of antihypertensive therapy with enalapril was evaluated in this animal model of chronic renal insufficiency. A dose of enalapril sufficient to prevent systemic hypertension normalized the glomerular capillary pressure without reducing the glomerular filtration rate in the remnant kidney. Maintenance of normal capillary pressure markedly reduced the development of proteinuria and sclerotic lesions in remnant glomeruli. These results suggest that antihypertensive therapy directed at reducing the glomerular capillary pressure could retard the progressive loss of renal function in patients whose functional renal mass has been reduced by disease.

[Drug treatment of chronic glomerulonephritis: contra]

It is controversial whether the pathomechanisms involved in chronic idiopathic glomerulonephritis are susceptible to therapeutic intervention. Etiological therapy, i.e. elimination of the responsible antigen, is possible only in exceptional cases, e.g. tropical diseases, infected ventriculoatrial shunt etc. Antiinflammatory therapy directed against pathomechanisms initiating or maintaining glomerular inflammation has an uncertain theoretical foundation because of lack of knowledge relating to the exact steps mediating tissue injury. Recent studies suggest keyroles for terminal components of complement system, products of lipoxygenase pathway of arachidonic acid and oxygen radicals-all of which are not readily influenced by available therapeutic modulaties. Finally, progression of glomerular inflammation to renal failure is usually not the cause of cumulative acute inflammatory glomerular lesions but rather the consequence of progressive sclerosis of glomeruli, arterioles and interstitium. As examples of controlled intervention trials, studies on extramembranous and membranoproliferative glomerulonephritis are discussed. The studies show limited and not always statistically significant influence on renal function, however, at the expense of considerable side effects. It is concluded that it is highly questionable whether inflammatory pathomechanisms are influenced by currently available drugs. However, therapeutic nihilism is not appropriate given modalities to influence mechanisms of nonspecific damage, e.g. by antihypertensive medication or dietary intervention.

Nephrotoxic serum nephritis with hypertension: amelioration by antihypertensive therapy

We have examined the effects of antihypertensive therapy on glomerular dynamics and on the clinical and morphologic features of a model of nephrotoxic serum nephritis (NSN) in which hypertension occurs. NSN was induced in uninephrectomized male Sprague Dawley rats, which drank 0.9% sodium chloride ad libitum. One-half were assigned randomly to a treated group whose blood pressure was normalized on a regimen of reserpine, hydralazine, and hydrochlorothiazide. Hypertension continued throughout the 6 weeks of study in untreated rats (blood pressure 148 +/- 5 vs. 103 +/- 3 mm Hg in treated rats, P less than 0.01). Urinary protein excretion was greater (437 +/- 110 vs. 254 +/- 81 mg/24 hr, P less than 0.005), and serum albumin lower (1.6 +/- 0.4 vs. 2.9 +/- 0.3 g/dl, P less than 0.01) in hypertensive animals. Diffuse glomerular endo- and extracapillary proliferation and arteriolar medial hypertrophy were observed frequently in nephritic rats with untreated hypertension. By contrast, structural abnormalities were limited primarily to focal segmental proliferation involving fewer than one-third of glomeruli in the absence of vascular changes in treated normotensive rats. Micropuncture studies performed 8 to 16 days after induction of nephritis showed a reduction in glomerular capillary pressure (46 +/- 1 vs. 55 +/- 1 mm Hg, P less than 0.001), glomerular plasma flow rate (115 +/- 20 vs. 160 +/- 20 nl/min, P less than 0.01), and single nephron filtration rate (42 +/- 4 vs. 56 +/- 5 nl/min, P less than 0.001) with antihypertensive treatment, suggesting that a hemodynamic mechanism may have been responsible for enhanced glomerular injury in the hypertensive nephritic animals.

Treatment of hypertension in renal disease

Experimental and clinical evidence are summarized that support the hypothesis that enhanced transmission of systemic hypertension to the adapted glomerulus in the setting of reduced nephron mass may be responsible for accelerated vascular and glomerular damage in the hypertensive stage of parenchymal renal disease in man. In experimental models of hypertension associated with reduced renal mass, the kidney appears to be damaged directly by transmission of pressure rather than primarily through vasoconstriction and ischemia. When hypertension is combined with models of glomerular disease, vascular and glomerular injury are aggravated. It is proposed that adaptive glomerular hemodynamic alterations which occur in parenchymal renal disease magnify the transmission of increased pressure and flows when hypertension supervenes. Accelerated vascular and glomerular damage and functional deterioration result. According to this hypothesis, control of systemic hypertension and minimization of hydraulic stress on the diseased glomerulus become critical to the management of chronic renal disease and the prevention of progressive renal insufficiency.

Mesangial immune injury, hypertension, and progressive glomerular damage in Dahl rats

Hypertension frequently accompanies chronic glomerulonephritis. Mesangial injury and glomerulosclerosis are common in glomerulonephritis and are often harbingers of progressive glomerular destruction. Thus, in a model of mesangial immune injury we studied the relationship between hypertension, mesangial injury, and glomerulosclerosis. We induced mesangial ferritin-antiferritin immune complex disease (FIC) in Dahl salt-sensitive (S) and salt-resistant (R) rats. S and R rats with FIC were fed chow containing 0.3% NaCl until 14 weeks of age and then switched to 8.0% NaCl chow until 28 weeks of age. Groups of control S and R rats (no FIC) were either fed 0.3% NaCl for 28 weeks or switched to 8.0% NaCl chow at 14 weeks of age. Blood pressure, serum creatinine, urinary protein, and glomerular injury (assessed by semiquantitative morphometric analysis) were determined at 14 and 28 weeks of age. R rats with or without FIC did not develop hypertension; mesangial injury was minimal. At 14 weeks of age, only S FIC rats developed hypertension, proteinuria, significant mesangial expansion and early glomerulosclerosis. At 28 weeks of age, proteinuria, mesangial expansion, and glomerulosclerosis were significantly more severe in hypertensive S rats with FIC than in those without FIC. These studies show that despite a normal salt intake, mesangial injury hastened the onset of hypertension, but only in rats genetically predisposed to hypertension (S FIC at 14 weeks). High dietary salt further aggravated hypertension, which, in turn, magnified both mesangial injury and glomerulosclerosis. Clinically, the different rates of progression of human glomerulonephritis associated with hypertension may be in part dependent on similar mechanisms.